Don't have a direct answer for you, but I imagine the following reference might be of some use if you can get a hold of it
S.B. Stringfellow, S. Gupta, C. Shaw, J.R. Alcock and R.W. Whatmore (2002) “Electrical conductivity control in uranium doped PbZrO3-PbTiO3-PbMg1/3Nb2/3O3 Pyroelectric Ceramics” J. European Ceram. Soc. 22 (4) 573-578